In recent years, there has been a remarkable reduction in the size of processing patterns used in semiconductor ICs, data storage media including hard disks, micro-machines, and other fields. Processing technologies, such as deposition and etching, used in these fields now require relatively broad irradiating energy beams such as high-density neutral particle beams or ion beams having high collimation (good directivity). The inventors of the present invention and others have already disclosed beam sources having the following constructions for such applications.
The first type of beam source comprises a discharge tube, a gas feed nozzle disposed upstream from the discharge tube for supplying gas therein, a beam-emitting electrode formed with a plurality of apertures and disposed on the downstream end of the discharge tube, and a plurality of electrodes disposed within the discharge tube. By applying a combination of different voltages to these electrodes, including a radio-frequency (RF) voltage, direct-current voltage, and ground voltage and by varying the type of gas introduced into the discharge tube, the beam source can generate different energy-level beams of differing types, such as positive ions, negative ions, neutral particles, radicals, and the like. A beam source of this construction is relatively compact and can be mounted on a manipulator to irradiate a beam onto a desired target in order to perform such localized processes on the target as deposition, etching, adhesion, bonding, and the like.
The second beam source is configured as the first with a nozzle disposed upstream from a cylindrical discharge tube for introducing gas therein, and a beam-emitting electrode (cathode) disposed downstream and formed with a plurality of apertures. This beam source also comprises an anode disposed in the discharge tube on the upstream end, a mechanism for applying a DC voltage across the anode and cathode, and an inductively coupled plasma-generating mechanism for converting gas in the discharge tube between these electrodes into plasma. A neutral particle beam source having this construction can generate high-density plasma from gas introduced into the discharge tube according to the inductively coupled high-frequency plasma-generating mechanism and can accelerate positive ions in the plasma on the cathode side using the two parallel electrodes. Charge exchange takes place in high-speed atom emission holes formed in the cathode on the downstream end, resulting in the emission of a neutral particle beam.
Unlike the above-described direct-current discharge beam source, this neutral particle beam source is provided with a plasma-generating section and an accelerating voltage section capable of generating high-density plasma at a low energy. Since a desired voltage from a low to a high voltage can be applied across the two electrodes, the beam source can generate a neutral particle beam at a desired energy level from a low energy to a high energy. Since the anode and cathode are disposed parallel to each other it is possible to generate a neutral particle beam with good directivity (collimation) and having a relatively high neutralization rate by controlling the length of the high-speed atom emission holes.
However, the above-described beam sources have not always been sufficient for forming high-density plasma and for efficiently extracting from this plasma an energy beam, such as an ion beam or neutral particle beam, having high directivity and high density.